1. Field of the Invention
The present invention relates to a pressure plate assembly for a friction clutch, comprising a housing arrangement; a pressure plate held in the housing arrangement with freedom to move in the same direction as that in which a rotational axis extends; a stored-energy element; a wear-compensating device acting in the path of force transmission between the stored-energy element and the pressure plate and/or between the stored-energy element and the housing arrangement, where the wear-compensating device has at least one adjusting element which can move in an adjusting direction to compensate for wear; and at least one spring element, which pretensions the minimum of one adjusting element for movement in the adjusting direction, where at least certain areas of the minimum of one spring element extend in the circumferential direction with respect to the rotational axis, and where the minimum of one spring element is provided with a support arrangement, which passes through at least certain areas of the spring.
2. Description of the Related Art
A pressure plate assembly in which the wear-compensating device has two adjusting rings which can be shifted in the circumferential direction with respect to each other is known from DE 197-12,888 A1. A helical tension spring is provided; the body of this helical spring with the helical turns extends along the inside circumferential surface of the adjusting rings; the first end of the spring has a connecting section, which is connected to one of the adjusting rings. The second end has a connecting section, which is used to connect the body of the helical spring to the pressure plate. Because this helical tension spring is relatively long in the circumferential direction, it is supported by appropriate support elements on both the radially inner and the radially outer sides. The support on the radially outer side in particular is accomplished by means of a separate support plate, provided on the pressure plate, which ultimately has the task of preventing the turns of the body of the helical spring from digging into the adjusting rings under the effect of centrifugal force while the clutch is operating in rotational mode. The provision or installation of a support plate such as this leads to increased cost and to extra labor.
A pressure plate assembly in which an adjusting element acting between the housing assembly and the stored-energy element is also under the action of a spring element is known from U.S. Pat. No. 5,409,091. The spring element is designed as a helical compression spring extending in the circumferential direction; a first connecting section is supported on the housing assembly, and the second connecting section is supported on a driver section cooperating with the adjusting element. A mandrel-like projection, formed as an integral part of the housing assembly and extending in the circumferential direction, passes all the way through the helical spring body of the spring element and thus supports the spring element especially in the radial direction.
An object of the present invention is to provide a pressure plate assembly in which the spring element which puts the wear-compensating device under pretension can be given radial support by simple measures.
According to the invention, the object is accomplished by a pressure plate assembly for a friction clutch, comprising a housing arrangement, a pressure plate held in the housing arrangement with freedom to move in the same direction as that in which a rotational axis extends, a stored-energy element, and a wear-compensating device acting in the path of force transmission between the stored-energy element and the pressure plate and/or between the stored-energy element and the housing arrangement, where the wear-compensating device has at least one adjusting element which can move in the adjusting direction to compensate for the wear and at least one spring element, which pretensions the minimum of one adjusting element for movement in the adjusting direction, where at least certain areas of the minimum of one spring element extend in the circumferential direction relative to the rotational axis, and where the minimum of one spring element is provided with a support arrangement, which passes at least through certain areas of the spring element.
It is also provided in accordance with the invention that the support arrangement is an integral part of the spring element.
In a departure from the approach followed in accordance with the state of the art, the present invention takes the route of integrating the support arrangement for the minimum of one spring element into the spring element itself. As a result, there is no need to make any changes to other components or to take special design measures on other components such as the housing arrangement or the pressure plate to obtain the desired circumferential support. This means, first, that it becomes much easier to produce a pressure plate assembly according to the invention and, second, that the design of the various components of the pressure plate assembly, especially the housing arrangement and the pressure plate, can be optimized with respect to other aspects, independently of the support measures to be provided for the minimum of one spring element.
For example, it can be provided that the minimum of one spring element has a helical spring body of plural spring turns with a first connector at a first end of the body and a second connector at a second opposite end of the body, the first and second connectors emerge from the spring turns at the corresponding two ends of the spring body. A section of material which essentially constitutes the support arrangement and which passes through the body of the helical spring emerges from one of the first and second connectors. Because spring elements of this type can usually be formed by bending pieces of spring steel wire, it is possible in this way, by providing an extended section of material which has no turns but which is instead surrounded by the turns of the body of the helical spring, to provide the required support.
It is also preferable for the section of material to extend beyond the first end and to have a third connector facing away from the second end, the third connector, e.g., being at a tip end of the material section. To prevent the occurrence of additional undesirable frictions or deformations in the area of the support arrangement or of the material section during operation, it is proposed that the third connector of the material section be connected to the same component as that to which the second connector is connected.
In the preferred embodiment of the pressure plate assembly according to the invention, it can be provided that the minimum of one adjusting element has an adjusting ring, which can be moved in the circumferential direction around the rotational axis to make the wear-compensating adjustment, and that the body of the helical spring of the minimum of one spring element extends in the circumferential direction along, or in the area of, the adjusting ring.
To prevent in particular a spring element of this type from digging into the adjusting device under the effect of centrifugal forces, it is proposed that the minimum of one spring element be located radially inside the adjusting ring and that the material section extend along a radially inner area (relative to the rotational axis) of the body of the helical spring of the minimum of one spring element.
The pressure plate assembly according to the invention can also be designed in such a way that the wear-compensating device acts between the pressure plate and the stored-energy element, and that the first connector of the minimum of one spring element is connected to the minimum of one adjusting element, whereas the second connector is connected to the pressure plate.
According to another aspect, the present invention pertains to a pretensioning spring for a pressure plate assembly with a wear-compensating device, which spring comprises a helical spring body of plural spring turns with a first connector at one end of the body and a second connector at a second opposite end of the body. A material section which emerges from one of the first and second connectors passes through the body of the helical spring. The material section has a third connector facing away from the spring body second end and located distal said body second end and said second connector. For example, the material section can emerge from the first connector, pass through the turns of the body and extend in a run a distance beyond the second connector, the third connector being at the tip end of the run.
The present invention also pertains to a friction clutch comprising at least one pretensioning spring according to the invention.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of the disclosure. For a better understanding of the invention, its operating advantages, and specific objects attained by its use, reference should be had to the drawing and descriptive matter in which there are illustrated and described preferred embodiments of the invention.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.